Conventional charging circuits include, for example, the charging device mentioned in Patent Document 1. In this charging device, a power generation element is connected to an electric storage element via a DC/DC converter. The power generation element is a photoelectric conversion element that converts irradiation light energy to electric power. The DC/DC converter supplies, to an electric storage element, the electric power generated in the photoelectric conversion element. The electric storage element stores the electric power supplied. As just described, the electric storage element can be charged by irradiating the photoelectric conversion element with light.